<HTML>
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A> 
</CENTER>






<HR>

<H3>pair_style awpmd/cut command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style awpmd/cut Rc keyword value ... 
</PRE>
<UL><LI>Rc = global cutoff, -1 means cutoff of half the shortest box length 

<LI>zero or more keyword/value pairs may be appended 

<LI>keyword = <I>hartree</I> or <I>dproduct</I> or <I>uhf</I> or <I>free</I> or <I>pbc</I> or <I>fix</I> or <I>harm</I> or <I>ermscale</I> or <I>flex_press</I> 

<PRE>  <I>hartree</I> value = none
  <I>dproduct</I> value = none
  <I>uhf</I> value = none
  <I>free</I> value = none
  <I>pbc</I> value = Plen
    Plen = periodic width of electron = -1 or positive value (distance units)
  <I>fix</I> value = Flen
    Flen = fixed width of electron = -1 or positive value (distance units)
  <I>harm</I> value = width
    width = harmonic width constraint
  <I>ermscale</I> value = factor
    factor = scaling between electron mass and width variable mass
  <I>flex_press</I> value = none 
</PRE>

</UL>
<P><B>Examples:</B>
</P>
<PRE>pair_style awpmd/cut -1
pair_style awpmd/cut 40.0 uhf free
pair_coeff * *
pair_coeff 2 2 20.0 
</PRE>
<P><B>Description:</B>
</P>
<P>This pair style contains an implementation of the Antisymmetrized Wave
Packet Molecular Dynamics (AWPMD) method.  Need citation here.  Need
basic formulas here.  Could be links to other documents.
</P>
<P>Rc is the cutoff.
</P>
<P>The pair_style command allows for several optional keywords
to be specified.
</P>
<P>The <I>hartree</I>, <I>dproduct</I>, and <I>uhf</I> keywords specify the form of the
initial trial wave function for the system.  If the <I>hartree</I> keyword
is used, then a Hartree multielectron trial wave function is used.  If
the <I>dproduct</I> keyword is used, then a trial function which is a
product of two determinants for each spin type is used.  If the <I>uhf</I>
keyword is used, then an unrestricted Hartree-Fock trial wave function
is used.
</P>
<P>The <I>free</I>, <I>pbc</I>, and <I>fix</I> keywords specify a width constraint on
the electron wavepackets.  If the <I>free</I> keyword is specified, then there is no
constraint.  If the <I>pbc</I> keyword is used and <I>Plen</I> is specified as
-1, then the maximum width is half the shortest box length.  If <I>Plen</I>
is a positive value, then the value is the maximum width.  If the
<I>fix</I> keyword is used and <I>Flen</I> is specified as -1, then electrons
have a constant width that is read from the data file.  If <I>Flen</I> is a
positive value, then the constant width for all electrons is set to
<I>Flen</I>.
</P>
<P>The <I>harm</I> keyword allow oscillations in the width of the
electron wavepackets.  More details are needed.
</P>
<P>The <I>ermscale</I> keyword specifies a unitless scaling factor
between the electron masses and the width variable mass.  More
details needed.
</P>
<P>If the <I>flex_press</I> keyword is used, then a contribution from the
electrons is added to the total virial and pressure of the system.
</P>
<P>This potential is designed to be used with <A HREF = "atom_style.html">atom_style
wavepacket</A> definitions, in order to handle the
description of systems with interacting nuclei and explicit electrons.
</P>
<P>The following coefficients must be defined for each pair of atoms
types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
above, or in the data file or restart files read by the
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
commands, or by mixing as described below:
</P>
<UL><LI>cutoff (distance units) 
</UL>
<P>For <I>awpmd/cut</I>, the cutoff coefficient is optional.  If it is not
used (as in some of the examples above), the default global value
specified in the pair_style command is used.
</P>
<HR>

<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
</P>
<P>The <A HREF = "pair_modify.html">pair_modify</A> mix, shift, table, and tail options
are not relevant for this pair style.
</P>
<P>This pair style writes its information to <A HREF = "restart.html">binary restart
files</A>, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.
</P>
<P>This pair style can only be used via the <I>pair</I> keyword of the
<A HREF = "run_style.html">run_style respa</A> command.  It does not support the
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
</P>
<HR>

<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "pair_coeff.html">pair_coeff</A>
</P>
<P><B>Default:</B>
</P>
<P>These are the defaults for the pair_style keywords: <I>hartree</I> for the
initial wavefunction, <I>free</I> for the wavepacket width.
</P>
</HTML>
